1. Field of the Invention
The present invention relates to an air conditioner in which the operation of the opening degree of a plurality of valves for controlling flow of refrigerant is improved, and a method of controlling the opening degree of the valves of the air conditioner.
2. Description of the Related Art
There have recently been increasing tendencies to use a gas heat pump type air conditioner using a gas engine as a driving source for driving a compressor in an outdoor unit. Such an air conditioner has an outdoor unit, an indoor unit and a controller for controlling the operation of the outdoor unit and the indoor unit. In some air conditioners, a plurality of (for example, five) electrically operated (motor-operated) valves for controlling the flow of refrigerant circulating in both the outdoor unit and the indoor unit are mounted in the outdoor unit, and these electrically operated valves are successively switched to control (perform the controlling operation on) the opening degree of each electrically operated valve.
The control operation of the opening degree of each of the plural electrically operated valves by the controller is performed as follows. Priorities are assigned to the respective electrically operated valves fixedly (with no alteration) in order of reducing the frequency of the controlling operation, and one operation time needed to perform the controlling operation of the opening degree of each electrically operated valve is set to a fixed time for each electrically operated valve, and the plural electrically operated valves are equally and time-divisionally controlled under the restriction on the operation time in order of decreasing precedence.
FIG. 1 is a flowchart showing the controlling operation of the opening degree of each electrically operated valve by the controller.
The controller assigns priorities to a main electrically operated valve, a first diversion electrically operated valve, a second diversion electrically operated valve, a third diversion electrically operated valve and a bypass electrically operated valve in this order, and sets the operation time needed to operate each electrically operated valve to 1000 msec, for example. As shown in FIG. 1, at the control start time of the electrically operated valve, the controller first clears a built-in timer (step S101), and operates the opening degree of the main electrically operated valve having the highest priority (step S102).
Subsequently, the controller judges whether the operation time elapses (step S103). The controller clears the timer just when the time-lapse of the operation time is judged (step S104), and operates the opening degree of the first diversion electrically operated valve having the second highest priority (step S105). Thereafter, the controller also judges whether the operation time elapses (step S106). It clears the timer just when the time-lapse of the operation time is judged. (step S107), and operates the opening degree of the second diversion electrically operated valve having the third highest priority (step S108). Further, as in the same manner as described above, the controller successively operates the opening degree of the third diversion electrically operated valve and the bypass electrically operated valve having the lower priorities in this order (step S109 to step S112). The controller returns to the step S101 just when the operation time of the bypass electrically operated valve elapses, and repeats the processing of the steps S101 to S112.
Since the controller controls the plural electrically operated valves as described above, when the opening degree of any electrically operated valve (for example, the main electrically operated valve) has reached a target opening degree within the one operation time (i.e., before the operation time elapses), the remaining time of the one operation time is wasted as a standby time for which no operation is carried on the main electrically operated valve. Therefore, the standby time of each electrically operated valve as described above finally causes increase of the total operation time needed to complete the operation of the opening degree for all the electrically operated valves, resulting in reduction of controllability of the electrically operated valves by the controller.
Further, the one-operation time which is needed to operate (control) the opening degree of each electrically operated valve once is settled to a fixed time uniformly among the electrically operated valves. Therefore, for example when the opening degree of any electrically operated valve (for example, the main electrically operated valve) cannot be set to a target opening degree within the one-operation time, the main electrically operated valve must wait for a next operation time which will come after the respective one-operation times for the first diversion electrically operated valve, the second diversion electrically operated valve, the third diversion electrically operated valve and the bypass electrically operated valve elapse. As a result, the control operation of the opening degree of the main electrically operated valve which must be originally instantaneously performed is delayed, resulting in reduction of controllability of the electrically operated valves by the controller.
Still further, when an electrically operated valve which is higher in operation frequency is varied in accordance with the operation situation of an air conditioner, for example, even when it becomes unnecessary to operate the first diversion electrically operated valve, the opening-degree controlling operation of the second diversion electrically operated valve, the third diversion electrically operated valve and the bypass electrically operated valve must wait until the one-operation time of the first diversion electrically operated valve elapses. Therefore, the operation of the second diversion electrically operated valve, the third diversion electrically operated valve and the bypass electrically operated valve is delayed, and thus the controllability of the electrically operated valves by the controller is reduced.